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89. Positioning synchro transmitter 7 and pointers 88
traveling yoke 15, which has a total longitudinal
and 89 are geared to friction roller 60 and follow-up
motion of approximately 1.10 inches along the radius
motor 9. Long pointer 89 makes one complete
of friction disk 30. The yoke is positioned along the
revolution every 100 rpm, and short pointer 88 makes
disk radius by lead screw 16, which is driven by
one complete revolution for full-scale indication. The
follow-up motor 9.
relative direction of the speed is indicated by the
Friction roller 60, integral with helical gear 28,
backing signal indicator, which is lighted only when
drives helical gear 32, which is mounted on, but free
the propeller shaft rotates in the astern direction.
to turn through a limited range about, input shaft 42.
Running synchro receiver 8 is driven electrically
Thus, the helical gear rotates at a speed proportional
by the associated shaft transmitter at a speed exactly
to the distance between the position of the roller on
one-tenth that of the propeller shaft. The running
the disk and the center of the disk. The radius of
synchro drives the input shaft of the speed-measuring
contact at any given point will determine the drive
mechanism through gear 118. The speed-measuring
ratio and speed at which roller 60, and gears 28 and 32
mechanism converts the rotary motions into
will rotate.
proportional angular displacements, Running synchro
The speed of helical gear 32 is automatically
8 also drives revolution counter 141 through gears at
adjusted to match the speed of running synchro driven
a speed exactly one-tenth that of the propeller speed.
gear 118 by the slip ring and contact assembly 39, the
The revolution counter registers the total propeller
upper two slip rings of which are mounted on the hub
revolutions directly, irrespective of the direction of
of gear 32 and are free to turn through a limited range
about input shaft 42. The assembly carries two outside
Positioning synchro transmitter 7 receives the
brush contacts, CW and CCW, each of which slides
angular displacement from the speed-measuring
on a slip ring. The center brush contact, C, slides on a
mechanism and transmits these displacements to the
slip ring, which is attached to hub 40 and is secured to
remotely located indicators.
input shaft 42 by friction thrust washer 54. The contact
assembly can be turned in either direction so that one
The speed-measuring mechanism operates on the
or the other of the outside contacts can mate with the
friction disk and roller assembly principle; that is, if a
center contact. This action energizes follow-up motor
disk is driven by a synchronous motor supplied with
9 and determines its direction of rotation.
a controlled frequency, the disk will run at a constant
speed irrespective of fluctuations of the ship's supply
When input gear 118 and helical gear 32 are
frequency. A roller placed in the center of the rotating
running at exactly the same speed, the contacts are
disk will not turn. However, if the roller is moved out
open, follow-up motor 9 is de-energized, and indicator
from the center of the disk, the roller will turn at a
pointers 88 and 89 are stationary. However, if the
speed that is proportional to the distance from the
speed of gear 118 changes, follow-up motor 9 is
center of the disk. For example, if the roller is moved
energized and drives lead screw 16, which moves yoke
out one-half inch from the center of the disk, the roller
15, in or out, depending on the direction of rotation, If
runs at twice the speed at which it ran when moved
the speed of gear 118 is faster than the original
one-fourth inch from the center of the disk. If the
balanced speed, the CW contacts close and, if the
position of the roller on the disk is varied, the speed
speed is lower, the CCW contacts close. The contacts
of the roller is varied in direct proportion to the
will remain closed to energize the follow-up motor in
distance the roller is positioned from the center of the
a correcting direction until the radius of disk contact
constmt-speed disk.
with roller 60 reaches a new value where the speed of
gear 32 is again equal to that of gear 118. At this point,
The friction disk and roller assembly also operates
the contacts open to de-energize the follow-up motor.
on the principle of comparing an unknown speed with
a known speed. The known speed in this case is
At zero (rpm) input from running synchro receiver
provided by synchronous motor 4, which drives
8, gear 118 is stationary and the contacts of the slip
friction disk 30 through gears at a constant speed. The
ring assembly will cause follow-up motor 9 to move
gearing is such that the disk speed is 16 2/3 rpm for
lead screw 16, forging friction roller 60 toward the
200 range units and 33 1/3 rpm for 400 range units.
center of friction disk 30. At the exact center, indicator
The friction disk is held in continuous contact with
pointers 88 and 89 should read zero rpm, and
friction roller 60, which is integral with helical gear
positioning synchro transmitter 7 should be on
28. The friction roller and helical gear are mounted on
electrical zero. However, the pointers will not reach

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